Charge densities and charge noise in mesoscopic conductors

We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom of this hierarchy are the partial density of states which represent the contribution to the local density of states if both the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements with a scanning tunneling microscope on multiprobe conductors in the presence of current flow. The partial density of states determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We introduce the off-diagonal elements of the partial density of states matrix to describe charge fluctuation processes. This generalization leads to a local Wigner-Smith life-time matrix.     

X射线Kirkpatrick-Baez显微镜用超反射镜的研制

 介绍了一种可应用于X射线Kirkpatrick-Baez（KB）显微镜的光学元件—X射线超反射镜。选用的W和B₄C作为镀膜材料,膜对数为20,采用单纯型调优的方法实现了X射线超反射镜设计,用磁控溅射的方法在Si基片上完成了W/B₄C X射线超反射镜的制备。采用高分辨率X射线衍射仪（8 keV）测量了X射线超反射镜的反射特性。制备的X射线超反射镜在掠入射角分别为1.052°和1.143°处,反射角度带宽为0.3°,反射率达到20%,可满足KB型显微镜的要求。     

金锥对靶背向超热电子分布的影响

 采用20 TW啁啾脉冲放大的ps激光辐照金锥靶和平面靶,对靶背向产生的超热电子角分布和能谱进行了实验研究。结果表明:金锥对超热电子的产生具有重要的影响。与平面靶情况相比,锥形靶靶背向产生的超热电子数量增加,电子能量为2.0~2.5 MeV的超热电子数目有大幅度增长;锥形靶背向超热电子的空间发散角大于平面靶,这是由于啁啾脉冲放大激光所固有的较高脉冲前沿产生的预等离子体造成的影响。     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子²⁰⁷Pb^q+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关. 关键词： 高电荷态离子 经典过垒模型 电子发射产额     

High longitudinal selectivity of shifting multiplexing in volume holograms

High longitudinal selectivity of the shifting multiplexing with spherical reference wave is proposed and demonstrated. A simplified method based on wave optics is used for calculating the selectivity, and the result fits well the experimental measurement. Under the paraxial condition, a simple formula for the longitudinal selectivity is introduced. With use of an object lens with effective NA=0.817, we obtain that an FWHM of selectivity is as small as 1 μm.     

Domain reversal behavior in perpendicular magnetic nanothin films

We report domain reversal behavior in perpendicular ferromagnetic nanothin films investigated by means of a novel magneto-optical microscope magnetometer, capable of grabbing domain reversal patterns in real time under an applied field as well as simultaneous measurements of 8000 local hysteresis loops with 400-nm special resolution. Three contrasting domain reversal behaviors are found to exist: wall-motion dominant, dendritic-growth dominant, and nucleation dominant reversal. Quantitative analysis reveals that the contrasting reversal behavior is mainly caused by a sensitive change in wall-motion speed and that the reversal ratio of wall-motion speed over nucleation rate is a governing parameter for the contrasting domain reversal dynamics. The activation volumes of the wall-motion and nucleation processes are found generally unequal, and the inequality is closely related with the domain dynamics. The domain reversal pattern is truly coincident with submicron-scale local coercivity variation and local switching time of domain evolution is exponentially dependent on local coercivity governed by a thermal activation relaxation process. The observed domain reversal behavior could be well predicted by a Monte Carlo simulation of a micromagnetic model based on the uniaxial magnetic anisotropy of nanothin films.     

On the solution of Fokker-Planck equation for electron transport

Two different techniques have been used to solve the Fokker-Planck equation for electron transport in infinite homogeneous medium namely, maximum entropy and flux-limited approach. The solutions obtained for the scalar flux function φ₀(x,s) by both methods are numerically compared.     

A vibrationally compensated far infrared laser interferometer for plasma density measurements

A modulated far-infrared laser interferometer which is presently operating on the PDX experiment at Princeton is described. The interferometer geometry permits the characterization of inside D, outside D as well as circular discharges. To achieve this versatility, a titanium corner cube reflector, mounted inside the PDX vacuum vessel is used in conjunction with a second visible wavelength interferometer for vibration corrections. In addition, the use of room temperature quasi-optical Schottky diodes in the far-infrared interferometer is reported. The minimum detectable line average density of the system is 5×10¹¹ cm^–3.